The international patent application published under number WO 95/29559 describes a multiplexing system for controlling plural channel processors. The multiplexing system is described with reference to FIG. 1 and includes:                a multiplexer (MUX) for providing a multiplexed signal (MS),        plural channel processors (CP[1] to CP[n]), each channel processor (CP[i]) having a control input, a data input for receiving an input signal (IS [i]), a complexity output for supplying a complexity signal representing the complexity of an associated input signal, and a data output for supplying an output data signal (OS[i]) to an associated input of the multiplexer, and        a bit rate allocator (CONT) responsive to the complexity signals, for supplying bit rate control signals to the associated control inputs of the channel processors as a function of the complexity signals, in such a manner that a bit rate (Rout[i]) of an output data signal (OS[i]) from a channel processor (CP[i]) is a function of the complexity of an associated input data signal and of the combination of the input data signals.        
In such a multiplexing system, the bit rate (Rout[i]) of an output data signal (OS[i]) from a channel processor (CP[i]) is equal to:
      Rout    ⁡          [      i      ]        =                    X        ⁡                  [          i          ]                                      ∑                      j            =            1                    n                ⁢                  X          ⁡                      [            j            ]                                ⁢    Rtot  where                i is the number of the channel processor,        X[i] is the complexity of the preceding group of pictures (hereinafter referred to as GOP) on a sliding window basis, i.e. the sum, for all the pictures of that GOP, of the product of the average quantization scale Qpic for a picture and the number of bits Tpic used to encode that picture:        
            X      ⁡              [        i        ]              =                  ∑        GOP            ⁢              Qpic        ·        Tpic              ,                Rtot is the total bit rate capacity available at the output of the multiplexer:        
  Rtot  =            ∑              i        =        1            n        ⁢                  Rout        ⁡                  [          i          ]                    .      